Time-resolved volumetric MRI in MRI-guided radiotherapy: an in-silico comparative analysis.
Abstract MRI-treatment units enable 2D cine-MRI centred in the tumour for motion detection in radiotherapy, but they lack 3D information due to spatio-temporal limits. To derive time-resolved 3D information, different approaches have been proposed in the literature, but a rigorous comparison among these strategies has not yet been performed. The goal of this study is to quantitatively investigate five published strategies that derive time-resolved volumetric MRI in MRI-guided radiotherapy: Propagation, out-of-plane motion compensation, Fayad model, ROI-based model and Stemkens model. Comparisons were performed usi...
Source: Physics in Medicine and Biology - July 19, 2019 Category: Physics Authors: Paganelli C, Portoso S, Garau N, Meschini G, Via R, Buizza G, Keall PJ, Riboldi M, Baroni G Tags: Phys Med Biol Source Type: research

Imaging of < sup > 99m < /sup > Tc-DMSA and < sup > 18 < /sup > F-FDG in humans using a Si/CdTe Compton camera.
Conclusions: To the best of our knowledge, for the first time, the current study demonstrates first time that the Si/CdTe Compton camera is capable of simultaneously imaging the distributions of two radiopharmaceuticals, 99mTc-DMSA and 18F-FDG, in a human body. These results suggest that the Si/CdTe Compton camera has the potential to become a novel modality for nuclear medical diagnoses enabling multi-probe simultaneous tracking.&amp;#13; &amp;#13. PMID: 31323647 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 19, 2019 Category: Physics Authors: Nakano T, Sakai M, Torikai K, Suzuki Y, Noda SE, Yamaguchi M, Takeda S, Nagao Y, Kikuchi M, Odaka H, Kamiya T, Kawachi N, Watanabe S, Arakawa K, Takahashi T Tags: Phys Med Biol Source Type: research

2D ultrasound imaging based intra-fraction respiratory motion tracking for abdominal radiation therapy using machine learning.
Abstract We have previously developed a robotic ultrasound imaging system for motion monitoring in abdominal radiation therapy. Owing to the slow speed of ultrasound image processing, our previous system could only track abdominal motions under breath-hold. To overcome this limitation, a novel 2D-based image processing method for tracking intra-fraction respiratory motion is proposed. Fifty-seven different anatomical features acquired from 27 sets of 2D ultrasound sequences were used in this study. Three 2D ultrasound sequences were acquired with the robotic ultrasound system from three healthy volunteers. The rem...
Source: Physics in Medicine and Biology - July 19, 2019 Category: Physics Authors: Huang P, Su L, Chen S, Cao K, Song Q, Kazanzides P, Iordachita I, Lediju Bell MA, Wong JW, Li D, Ding K Tags: Phys Med Biol Source Type: research

The dielectric properties of skin and their influence on the delivery of tumor treating fields to the torso: a study combining < i > in vivo < /i > measurements with numerical simulations.
This study provides a new insight into the role of skin in determining the distribution of TTFields within the body. PMID: 31323651 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 19, 2019 Category: Physics Authors: Hershkovich HS, Urman N, Yesharim O, Naveh A, Bomzon Z Tags: Phys Med Biol Source Type: research

Impacts of photon counting CT to maximum intensity projection (MIP) images of cerebral CT angiography: theoretical and experimental studies.
Abstract While CTA is an established clinical gold standard for imaging large cerebral arteries and veins, an important challenge that currently remains for CTA is its limited performance in imaging small perforating arteries with diameters below 0.5 mm. The purpose of this work was to theoretically and experimentally study the potential benefits of using photon counting detector (PCD)-based CT (PCCT) to improve the performance of CTA in imaging these small arteries. In particular, the study focused on an important component of the CTA image package known as the maximum intensity projection (MIP) image. To help un...
Source: Physics in Medicine and Biology - July 17, 2019 Category: Physics Authors: Harvey E, Feng M, Ji X, Zhang R, Li Y, Chen GH, Li K Tags: Phys Med Biol Source Type: research

Dynamic beam current control for improved dose accuracy in PBS proton therapy.
Abstract The step-and-shoot method of pencil beam scanning delivers the dose on a three-dimensional grid in the target volume, with one dimension defined by the proton energy. While the dose per pencil beam may vary substantially within an iso-energy layer, the beam current typically remains constant. In this static operation mode, the inherent latency of the beam switch-off mechanism results in a lower limit for the deliverable spot dose, which may prevent the application of some of the low-weighted spots prescribed by the treatment planning system. To overcome this limitation, we introduced dynamic beam current ...
Source: Physics in Medicine and Biology - July 17, 2019 Category: Physics Authors: Bula C, Belosi MF, Eichin M, Hrbacek J, Meer D Tags: Phys Med Biol Source Type: research

Non-invasive determination of blood input function to compute rate of myocardial glucose uptake from dynamic FDG PET images of rat heart in vivo: comparative study between the inferior vena cava and the left ventricular blood pool with spill over and partial volume corrections.
Abstract The purpose of this work was to compute blood input function from the inferior vena cava (IVC) with partial volume (PV) corrections and compare to that obtained from the left ventricular blood pool (LVBP) with spill-over (SP) and partial volume (PV) corrections. These were then used to compute and validate rates of myocardial 2-deoxy-2-[18F]fluoro-D-glucose (FDG) uptake (Ki) from dynamic positron emission tomography (PET) images of rat hearts in vivo in comparison to that obtained from invasive arterial blood sampling. Whole body 60 minute dynamic FDG PET/CT imaging of n=8 control Wistar Kyoto (WKY) rats ...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Huang Q, Massey JC, Minczuk K, Li J, Kundu BK Tags: Phys Med Biol Source Type: research

Predicting lung nodule malignancies by combining deep convolutional neural network and handcrafted features.
Abstract To predict lung nodule malignancy with a high sensitivity and specificity, we propose a fusion algorithm that combines handcrafted features (HF) into the features learned at the output layer of a 3D deep convolutional neural network (CNN). First, we extracted twenty-nine handcrafted features, including nine intensity features, eight geometric features, and twelve texture features based on grey-level co-occurrence matrix (GLCM) averaged from five grey levels, four distances and thirteen directions. We then trained 3D CNNs modified from three 2D CNN architectures (AlexNet, VGG-16 Net and Multi-crop Net) to ...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Li S, Xu P, Li B, Chen L, Zhou Z, Hao H, Duan Y, Folkert MR, Ma J, Huang S, Jiang SB, Wang J Tags: Phys Med Biol Source Type: research

EPR-imaging of magnetic field effects on radiation dose distributions around millimeter-size air cavities.
r M Abstract New hybrid radiotherapy treatment systems combining an MRI-scanner with a source of ionizing radiation are being introduced in the clinic. The strong magnetic fields of MRI considerably affect radiation dose distributions, especially at tissue-air interfaces due to the electron return effect (ERE). Experimental investigation of the ERE within a sub-millimeter thick surface layer is still highly challenging. &amp;#13; In the present work, we examine and quantify the magnetic field induced perturbations of dose distributions within a 0.5 mm layer surrounding millimeter-size air cavities by applying ...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Höfel S, Fix MK, Zwicker F, Sterpin E, Drescher M Tags: Phys Med Biol Source Type: research

An investigation of quantitative accuracy for deep learning based denoising in oncological PET.
Abstract Reducing radiation dose is important for PET imaging. However, reducing injection doses causes increased image noise and low signal-to-noise ratio (SNR), subsequently affecting diagnostic and quantitative accuracies. Deep learning methods have shown a great potential to reduce the noise and improve the SNR in low dose PET data. &amp;#13; In this work, we comprehensively investigated the quantitative accuracy of small lung nodules, in addition to visual image quality, using deep learning based denoising methods for oncological PET imaging. We applied and optimized an advanced deep learning method based...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Lu W, Onofrey JA, Lu Y, Shi L, Ma T, Liu Y, Liu C Tags: Phys Med Biol Source Type: research

Magnetic resonance electrical property mapping at 21.1 T: a study of conductivity and permittivity in phantoms, < i > ex vivo < /i > tissue and < i > in vivo < /i > ischemia.
This report investigates the feasibility and accuracy of EPT at 21.1 T for multiple RF coils and modes of operation using phantoms. Additionally, it demonstrates the EP of the &amp;lt;i&amp;gt;in vivo&amp;lt;/i&amp;gt; rat brain with and without ischemia. &amp;#13; &amp;#13; Helmholtz-based EPT was implemented in its Full-form, which demands the complex &amp;lt;i&amp;gt;B&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt;&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt;&amp;lt;/i&amp;gt; field, and a simplified form requiring either just the &amp;lt;i&amp;gt;B&...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Amouzandeh G, Mentink-Vigier F, Helsper S, Bagdasarian FA, Rosenberg JT, Grant S Tags: Phys Med Biol Source Type: research

Anatomical deformation due to horizontal rotation: towards gantry-free radiation therapy.
This study aims to understand and quantify anatomical deformations caused by horizontal rotation with scan sequences sufficiently short to facilitate integration into an MRI-guided workflow.&amp;#13; &amp;#13; Rigid and non-rigid pelvic deformations due to horizontal rotation were quantified for a cohort of 8 healthy volunteers using a bespoke patient rotation system and a clinical MRI scanner. For each volunteer a reference scan was acquired at 0° followed by sequential faster scans in 45° increments through to 360°. All fast scans were registered to the 0° image via a 3-step process: First, images...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Buckley JG, Rai R, Liney GP, Dowling JA, Holloway L, Metcalfe P, Keall PJ Tags: Phys Med Biol Source Type: research

Cone-beam computed tomography-based delta-radiomics for early response assessment in radiotherapy for locally advanced lung cancer.
Abstract Cone-beam computed tomography (CBCT) images acquired during radiotherapy may allow early response assessment. Previous studies have reported inconsistent findings on an association of CBCT-measured tumor volume changes with clinical outcomes. The purpose of this pilot study was twofold: (1) to characterize changes in CBCT-based radiomics features during treatment; and (2) to quantify the potential association of CBCT-based delta-radiomics features with overall survival in locally advanced lung cancer.&amp;#13; &amp;#13; We retrospectively identified 23 patients and calculated 658 radiomics feature...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Shi L, Rong Y, Daly M, Dyer BA, Benedict S, Qiu J, Yamamoto T Tags: Phys Med Biol Source Type: research

First measurements with a plastic scintillation dosimeter at the Australian MRI-LINAC.
Abstract MRI-LINACs combine MRI and LINAC technologies with the potential for image guided radiation therapy with optimal soft-tissue contrast. In this work, we present the advantages and limitations of plastic scintillation dosimeters (PSDs) for relative dosimetry with MRI-LINACs. PSDs possess many desirable qualities, including magnetic field insensitivity and irradiation angle independence, which are expected to make them suitable for dosimetry with MRI-LINACs. An in-house PSD was used to measure field size output factors as well as a percent depth dose distribution and the beam quality index TPR(20/10) at 10.5...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Madden L, Archer J, Li E, Jelen U, Dong B, Roberts NF, Holloway L, Rozenfeld AB Tags: Phys Med Biol Source Type: research

Inverse Compton radiation: a novel X-ray source for K-edge subtraction angiography?
ibi A Abstract Coronary angiography is clinically used worldwide to diagnose diseases of coronary arteries. Despite its effectiveness, this technique is quite invasive and it is associated to significant risks due to the arterial catheterisation needed to inject the contrast agent. A valid alternative is using the K-edge subtraction method, which is based on the subtraction of two images acquired at energies bracketing the K-edge of the contrast element. The enhanced sensitivity of K-edge subtraction allows the intravenous injection of the contrast agent, thus reducing the risks of catheterisation. This technique ...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Paternò G, Cardarelli P, Gambaccini M, Serafini L, Petrillo V, Drebot I, Taibi A Tags: Phys Med Biol Source Type: research

ML-EM algorithm for dose estimation using PET in proton therapy.
Abstract Positron emission tomography (PET) has been extensively studied and clinically investigated for dose verification in proton therapy. However, the production distributions of positron emitters are not proportional to the dose distribution. Thus, direct dose evaluation is limited when using the conventional PET-based approach. We propose a method for estimating the dose distribution from the positron emitter distributions using the maximum likelihood (ML) expectation maximization (EM) algorithm combined with filtering. In experiments to verify the effectiveness of the proposed method, mono-energetic and spr...
Source: Physics in Medicine and Biology - July 15, 2019 Category: Physics Authors: Masuda T, Nishio T, Kataoka J, Arimoto M, Sano A, Karasawa K Tags: Phys Med Biol Source Type: research

Determining dose enhancement factors of high-Z nanoparticles from simulations where lateral secondary particle disequilibrium exists.
Abstract Nanoparticles containing high atomic number (high-Z) materials have been shown to enhance the radiobiological effectiveness of ionizing radiation. This effect is often attributed to an enhancement of the absorbed dose in the vicinity of the nanoparticles, based on Monte Carlo simulations that show a significant local enhancement of the energy deposition on the microscopic scale. The results of such simulations may be significantly biased and lead to a severe overestimation of the dose enhancement if the condition of secondary particle equilibrium is not met in the simulation setup. This current work shows...
Source: Physics in Medicine and Biology - July 13, 2019 Category: Physics Authors: Rabus H, Gargioni E, Li WB, Nettelbeck H, Villagrasa C Tags: Phys Med Biol Source Type: research

Electronics method to advance the coincidence time resolution with bismuth germanate.
Abstract Exploiting the moderate Cherenkov yield from 511 keV photoelectric interactions in bismuth germanate (BGO) scintillators enables one to achieve a level of coincidence time resolution (CTR) appropriate for time-of-flight positron emission tomography (TOF-PET). For this approach, owing to the low number of promptly emitted light photons, single photon time resolution (SPTR) can have a stronger influence on achievable CTR. We have previously shown readout techniques that reduce effective device capacitance of large area silicon photomultipliers (SiPMs) can yield improvements in single photon response shape t...
Source: Physics in Medicine and Biology - July 13, 2019 Category: Physics Authors: Cates JW, Levin CS Tags: Phys Med Biol Source Type: research

Three-dimensional convolutional neural networks for simultaneous dual-tracer PET imaging.
In this study, we present a hybrid loss-guided deep learning based framework for dual-tracer PET imaging using sinogram data, which can achieve reconstruction by naturally unifying two functions: the reconstruction of the mixed images and the separation of each tracer. Combined with volumetric dual-tracer images, we adopted a three-dimensional (3D) convolutional neural network (CNN) to learn full features, including spatial information and temporal information simultaneously. In addition, an auxiliary loss layer was introduced to guide the reconstruction of the dual tracers. We used Monte Carlo simulations with data augmen...
Source: Physics in Medicine and Biology - July 11, 2019 Category: Physics Authors: Xu J, Liu H Tags: Phys Med Biol Source Type: research

Radio-enhancement by gold nanoparticles and their impact on water radiolysis for x-ray, proton and carbon-ion beams.
Abstract Gold nanoparticle (GNP) radio-enhancement is a promising technique to increase the dose deposition in a tumor while sparing neighboring healthy tissue. Previous experimental studies showed effects on cell survival and tumor control for keV x-rays but surprisingly also for MV-photons, proton and carbon-ion beams. In a systematic study, we use the Monte Carlo simulation tool TOPAS-nBio to model the GNP radio-enhancement within a cell as a function of GNP concentration, size and clustering for a wide range of energies for photons, protons and, for the first time, carbon-ions. Moreover, we include water radio...
Source: Physics in Medicine and Biology - July 11, 2019 Category: Physics Authors: Rudek B, McNamara AL, Ramos-Mendez J, Byrne H, Kuncic Z, Schuemann J Tags: Phys Med Biol Source Type: research

Known-component metal artifact reduction (KC-MAR) for cone-beam CT.
Conclusions. The KC-MAR algorithm combines knowledge of surgical instrumentation with 3D image reconstruction in a manner that overcomes potential pitfalls of segmentation. The approach is compatible with FBP - thereby maintaining simplicity in a manner that is consistent with surgical workflow - or more sophisticated model-based reconstruction methods that could further improve image quality and/or help reduce radiation dose.&amp;#13. PMID: 31287092 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 9, 2019 Category: Physics Authors: Uneri A, Zhang X, Yi T, Stayman JW, Helm PA, Osgood GM, Theodore N, Siewerdsen JH Tags: Phys Med Biol Source Type: research

Accuracy of kidney dosimetry performed using simplified time activity curve modelling methods: a < sup > 177 < /sup > Lu-DOTATATE patient study.
Accuracy of kidney dosimetry performed using simplified time activity curve modelling methods: a 177Lu-DOTATATE patient study. Phys Med Biol. 2019 Jul 09;: Authors: Zhao W, Esquinas PL, Frezza A, Hou X, Beauregard JM, Celler A Abstract &amp;lt;sup&amp;gt;177&amp;lt;/sup&amp;gt;Lu-DOTATATE therapy has been shown to produce encouraging results in treatment of neuroendocrine tumours (NETs). Unfortunately, since dosimetry for radionuclide therapy is considered to be challenging, typically similar amount of radiopharmaceutical is administered to every patient. There is growing evidence that...
Source: Physics in Medicine and Biology - July 9, 2019 Category: Physics Authors: Zhao W, Esquinas PL, Frezza A, Hou X, Beauregard JM, Celler A Tags: Phys Med Biol Source Type: research

Super-resolution X-ray phase-contrast and dark-field imaging with a single 2D grating and electromagnetic source stepping.
Abstract Here we report a method for increased resolution of single exposure three modality X-ray images using Super-Resolution. The three X-ray image modalities are absorption-, differential phase-contrast-, and dark-field-images. To create Super- Resolution, a non-mechanically movable micro-focus X-ray source is used. A series of almost identical X-ray projection images is obtained while the point source is translated in a two-dimensional grid pattern. The three image modalities are extracted from Fourier space using spatial harmonic analysis, also known as the single-shot method. Using Super-Resolution on the l...
Source: Physics in Medicine and Biology - July 8, 2019 Category: Physics Authors: Rix KR, Dreier T, Shen T, Bech M Tags: Phys Med Biol Source Type: research

On the spectral characterization of radiochromic films irradiated with clinical proton beams.
o T, Khan R Abstract Radiochromic films have been widely studied for clinical dosimetry in conventional external beam radiation therapy. With an increase in practice of proton therapy, such films are being conveniently used; however, their spectroscopic characterization for this modality is lacking. This work investigated the response of the EBT3 radiochromic films irradiated in a Mevion S250™ clinical proton beam. Dose, dose rate, inter-batch, sensitivity, and linear energy transfer (LET) dependencies of the films were studied. Pieces of the radiochromic films from different batches were irradiated using a ...
Source: Physics in Medicine and Biology - July 5, 2019 Category: Physics Authors: Darafsheh A, León-Marroquín EY, Mulrow DJ, Baradaran-Ghahfarokhi M, Zhao T, Khan R Tags: Phys Med Biol Source Type: research

Navigated non-contact fluorescence tomography.
Abstract A non-contact approach for diffuse optical tomography (DOT) has been developed for on-demand image updates using surgical navigation technology. A stereoscopic optical tracker provides real-time localization of reflective spheres mounted to a laser diode and near-infrared camera. Standard camera calibration is combined with tracking data to determine the intrinsic camera parameters (focal length, principal point and non-linear lens distortion) and the tracker-to-camera transform. Tracker-to-laser calibration is performed using images of laser beam intersection with a tracked calibration surface. Source an...
Source: Physics in Medicine and Biology - July 5, 2019 Category: Physics Authors: Daly MJ, Wilson BC, Irish JC, Jaffray DA Tags: Phys Med Biol Source Type: research

Large energy acceptance gantry for proton therapy utilizing superconducting technology.
We describe the iterative process we have applied to design the magnets and the beam transport, for which we have used different codes. &amp;lt;i&amp;gt;COSY Infinity&amp;lt;/i&amp;gt; and &amp;lt;i&amp;gt;OPAL&amp;lt;/i&amp;gt; have been used to design the beam transport optics and to track the particles in the magnetic fields, which are produced by the magnets designed in &amp;lt;i&amp;gt;Opera&amp;lt;/i&amp;gt;. With beam optics calculations we have derived an optimal achromatic beam transport with the large momentum acceptance of the proton pencil beam and we show the agr...
Source: Physics in Medicine and Biology - July 4, 2019 Category: Physics Authors: Nesteruk KP, Calzolaio C, Meer D, Rizzoglio V, Seidel M, Schippers JM Tags: Phys Med Biol Source Type: research

Leuco crystal violet-Pluronic F-127 3D radiochromic gel dosimeter.
Abstract This work reports results related to the manufacturing and optimisation of a leuco crystal violet (LCV)-Pluronic F-127 radiochromic gel dosimeter suitable for 3D radiotherapy dosimetry. A feature of this gel is that the natural gelatine polymer, which is most often used as a matrix in 3D dosimeters, is substituted with Pluronic F-127 synthetic copolymer (poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide). Pluronic F-127 ensures a higher transparency than gelatine, which may be beneficial for optical computed tomography readout, and improves the thermal properties in the temperatur...
Source: Physics in Medicine and Biology - July 4, 2019 Category: Physics Authors: Kouvati K, Jaszczak M, Papagiannis P, Kadlubowski S, Wach R, Maras P, Dudek M, Kozicki M Tags: Phys Med Biol Source Type: research

Impact of image preprocessing on the scanner dependence of multi-parametric MRI radiomic features and covariate shift in multi-institutional glioblastoma datasets.
Abstract Recent advances in radiomics have enhanced the value of medical imaging in various aspects of clinical practice, but a crucial component that remains to be investigated further is the robustness of quantitative features to imaging variations and across multiple institutions. In the case of MRI, signal intensity values vary according to the acquisition parameters used, yet no consensus exists on which preprocessing techniques are favorable in reducing scanner-dependent variability of image-based features. Hence, the purpose of this study was to assess the impact of common image preprocessing methods on the...
Source: Physics in Medicine and Biology - July 4, 2019 Category: Physics Authors: Um H, Tixier F, Bermudez D, Deasy JO, Young RJ, Veeraraghavan H Tags: Phys Med Biol Source Type: research

Fully automatic catheter segmentation in MRI with 3D convolutional neural networks: application to MRI-guided gynecologic brachytherapy.
In conclusion, to the best of our knowledge, fully automatic segmentation of multiple closely spaced catheters from intraoperative MR images was achieved for the first time in gynecological brachytherapy. PMID: 31272095 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 4, 2019 Category: Physics Authors: Zaffino P, Pernelle G, Mastmeyer A, Mehrtash A, Zhang H, Kikinis R, Kapur T, Spadea MF Tags: Phys Med Biol Source Type: research

Characterization of a new tissue equivalent proportional counter for dosimetry of neutron and photon fields: Comparison of measurements and Monte Carlo simulations.
Abstract The tissue equivalent proportional counter (TEPC) is widely recognized as an important dosimetric technique particularly for complex radiation fields. The Korea Astronomy and Space Science Institute has recently developed a new spherical TEPC to monitor the space radiation environment in the low earth orbit. The purpose of this study is to examine the performance of the TEPC against standard photon (137Cs) and neutron (252Cf) sources through ground-based measurements and Monte Carlo simulations prior to its actual implementation. Lineal energy distributions, microdosimetric spectra and dosimetric quantiti...
Source: Physics in Medicine and Biology - July 3, 2019 Category: Physics Authors: Malimban J, Nam UW, Pyo J, Youn S, Ye SJ Tags: Phys Med Biol Source Type: research

Biomechanical modeling of neck flexion for deformable alignment of the salivary glands in head and neck cancer images.
Abstract During head and neck (HN) cancer radiation therapy (RT), dose-response analysis for the parotid glands (PG) relies on accurate alignment of soft tissue between longitudinal images. To isolate the response of the PG to delivered dose, from deformation due to patient position, patient postural changes, mainly due to neck flexion, should be resolved. A biomechanical model-based deformable image registration (DIR) algorithm was evaluated to estimate the displacements and deformations of the PGs due to postural changes. Eighty-two CT image pairs of HN cancer patients with varying neck flexion angles were obtai...
Source: Physics in Medicine and Biology - July 3, 2019 Category: Physics Authors: McCulloch M, Anderson BM, Cazoulat G, Peterson CB, Mohamed ASR, Volpe S, Elhalawani HM, Bahig H, Rigaud B, King J, Ford A, Fuller CD, Brock KK Tags: Phys Med Biol Source Type: research

Extended field radiotherapy measurements in a single shot using a BaFBr-based OSL-film.
Abstract This work evaluated the use of a class solution specific calibration for an extra-large BaFBr based Optically Stimulated Luminescence film (OSL; 43x35cm²; Zeff =4.55). The clinical need for such large dosimeters follows from the increased use of extended-field radiation therapy (EFRT). E.g. for prostate cancer EFRT is currently used in the first prospective trial investigating the benefit of adding elective irradiation of the para-aortic lymph nodes in PN1 prostate cancer. The full extent of these EFRT dose distributions is not covered by the well-established standard sized radiochromic film or 2D de...
Source: Physics in Medicine and Biology - July 3, 2019 Category: Physics Authors: De Roover R, Berghen C, De Meerleer G, Depuydt T, Crijns W Tags: Phys Med Biol Source Type: research

Development of advanced skin dose evaluation technique using a tetrahedral-mesh phantom in external beam radiotherapy: a Monte Carlo simulation study.
This study aims to develop a technique to evaluate accurate skin dose using the TM phantom in RT. The TM phantom was modeled with thin skin layers, including the epidermis, basal layer, and dermis from CT images. Using the Geant4 toolkit, the simulation was performed to evaluate the skin dose according to the radiation treatment conditions. The skin dose was evaluated at a surface depth of 50 μm and 2,000 μm. The difference in average skin dose between depths was up to 37%, depending on the thickness and region of the skin to be measured. The results indicate that the skin dose has been overestimated when the skin is...
Source: Physics in Medicine and Biology - July 3, 2019 Category: Physics Authors: Cheon BW, Yoo DH, Shin WG, Choi HJ, Park H, Kim JI, Min CH Tags: Phys Med Biol Source Type: research

Image reconstruction for interrupted-beam X-ray CT on diagnostic clinical scanners.
Abstract Low-dose X-ray CT is a major research area with high clinical impact. Compressed sensing using view-based sparse sampling and sparsity-promoting regularization has shown promise in simulations, but these methods can be difficult to implement on diagnostic clinical CT scanners since the X-ray beam cannot be switched on and off rapidly enough. An alternative to view-based sparse sampling is interrupted-beam sparse sampling. SparseCT is a recently-proposed interrupted-beam scheme that achieves sparse sampling by blocking a portion of the beam using a multislit collimator. The use of a multislit collimator ne...
Source: Physics in Medicine and Biology - July 1, 2019 Category: Physics Authors: Muckley MJ, Chen B, Vahle T, O'Donnell T, Knoll F, Sodickson A, Sodickson D, Otazo R Tags: Phys Med Biol Source Type: research

Spatial signature of dose patterns associated with acute radiation-induced lung damage in lung cancer patients treated with Stereotactic Body Radiation Therapy.
Abstract Thoracic Radiation Therapy (RT) is often associated with lung side effects, whose etiology is still controversial. Our aim was to explore correlations between local dose in the thoracic anatomy and the Radiation-Induced Lung Damage (RILD). To this end, we designed a robust scheme for Voxel-Based Analysis (VBA) to explore dose patterns associated with RILD in non-small-cell lung cancer (NSCLC) patients receiving Stereotactic Body RT (SBRT).&amp;#13; We analyzed 106 NSCLC SBRT patients (median prescription dose: 50 Gy; range: [40-54] Gy) in 4 fractions (range: [3-5]) with clinical and dosimetric records...
Source: Physics in Medicine and Biology - July 1, 2019 Category: Physics Authors: Palma G, Monti S, Thor M, Rimner A, Deasy JO, Cella L Tags: Phys Med Biol Source Type: research

Dose to water versus dose to medium from cavity theory applied to small animal irradiation with kilovolt x-rays.
Abstract Dose reporting is a matter of concern in the preclinical field as the different dose descriptors dose-to-water-in-medium (&amp;lt;i&amp;gt;D&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;wm&amp;lt;/sub&amp;gt;) and dose-to-medium-in-medium (&amp;lt;i&amp;gt;D&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;mm&amp;lt;/sub&amp;gt;) coexist. For kV photons differences between both quantities are expected to be amplified due to photon energy absorption coefficients differences for different media, and could represent a limiting factor for accurate translation of precl...
Source: Physics in Medicine and Biology - June 28, 2019 Category: Physics Authors: Vaniqui A, Walters B, Fonseca GP, Verhaegen F Tags: Phys Med Biol Source Type: research

Task-based image quality assessment in radiation therapy: initial characterization and demonstration with computer-simulation study.
Abstract In the majority of current radiation therapy (RT) applications, image quality is still assessed subjectively or by utilizing physical measures. A novel theory that applies objective task-based image quality assessment in radiation therapy (IQA-in-RT) was recently proposed, in which the area under the therapeutic operating characteristic curve (AUTOC) was employed as the figure-of-merit (FOM) &amp;#13; for evaluating RT effectiveness. Although theoretically more appealing than conventional subjective or physical measures, a comprehensive implementation and evaluation of this novel task-based IQA-in-RT ...
Source: Physics in Medicine and Biology - June 28, 2019 Category: Physics Authors: Dolly S, Lou Y, Anastasio MA, Li H Tags: Phys Med Biol Source Type: research

Evaluating a potential technique with local optical flow vectors for automatic organ-at-risk (OAR) intrusion detection and avoidance during radiotherapy.
Abstract Various techniques of deep inspiration breath hold (DIBH) have been used to mitigate the likelihood and risk of exposing the heart, an organ-at-risk (OAR) for unintended radiation during left breast radiotherapy. However, issues of reproducibility of these techniques warrant further investigation into the feasibility of detecting the intrusion of an OAR into the treatment field during intra-fractional treatment delivery. The increase of high-dose, low-fraction radiotherapy treatments makes it important to immediately adapt treatment once an organ-at-risk (OAR) is detected in the treatment field. This proo...
Source: Physics in Medicine and Biology - June 28, 2019 Category: Physics Authors: Teo PT, Guo K, Ahmed B, Alayoubi N, Kehler K, Fontaine G, Sasaki D, Pistorius S Tags: Phys Med Biol Source Type: research

Development and evaluation of anisotropic and nonlinear aortic models made from clinical images for in vitro experimentation.
Abstract In this work we developed a methodology to manufacture a new type of arterial model that could be used in experimental setting instead of excised arteries while developing new imaging modalities. CT-images of the descending aorta were used to create molds with patient specific morphology. A Polyvinyl Alcohol (PVA) solution with a reinforcing cotton mesh was used to generate the models. The mesh is circumferentially elastic while non-compliant longitudinally and is responsible for the non-linear anisotropic mechanical behavior of the models. Two models were fabricated following the same manufacturing proce...
Source: Physics in Medicine and Biology - June 28, 2019 Category: Physics Authors: Bernal M, Saldarriaga J, Cabeza C, Negreira C, Bustamante J, Brum J Tags: Phys Med Biol Source Type: research

Automatic pedicle screw planning using atlas-based registration of anatomy and reference trajectories.
Conclusions. The algorithm demonstrated accurate, automatic definition of pedicle screw trajectories, diameter, and length in CT images of the spine without segmentation. The studies support translation to clinical studies in free-hand or robot-assisted spine surgery, quality assurance, and data analytics in which fast trajectory definition is a benefit to workflow. &amp;#13. PMID: 31247607 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 27, 2019 Category: Physics Authors: Vijayan R, De Silva T, Han R, Zhang X, Uneri A, Doerr S, Ketcha MD, Perdomo-Pantoja A, Theodore N, Siewerdsen JH Tags: Phys Med Biol Source Type: research

Effective dose conversion coefficient for gamma ray exposure from an overhead plume.
This study demonstrates an accurate method for calculating the effective dose to the ground receptor from an external plume which can be further applied for any radionuclide under any meteorological condition. PMID: 31239410 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Dey R, Patni HK, Singh KD, Kulkarni MS, Anand S Tags: Phys Med Biol Source Type: research

Automatic segmentation of the mandible from computed tomography scans for 3D virtual surgical planning using the convolutional neural network.
Abstract Segmentation of mandibular bone in CT scans is crucial for 3D virtual surgical planning of craniofacial tumor resection and free flap reconstruction of the resection defect, in order to obtain a detailed surface representation of the bones. A major drawback of most existing mandibular segmentation methods is that they require a large amount of expert knowledge for manual or partially automatic segmentation. In fact, due to the lack of experienced doctors and experts, high quality expert knowledge is hard to achieve in practice. Furthermore, segmentation of mandibles in CT scans is influenced seriously by ...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Qiu B, Guo J, Kraeima J, Glas HH, Borra RJH, Witjes MJH, van Ooijen PMA Tags: Phys Med Biol Source Type: research

Image reconstruction by Mumford-Shah regularization for low-dose CT with multi-GPU acceleration.
Abstract Mumford-Shah (MS) functional has emerged as a regularization technique in X-ray computed tomography (CT) recently. However, for high-resolution CT applications, the huge size of both projection data and image leads to an implementation difficulty. In this work, we propose an approach to implement and accelerate MS regularization on a multi-GPU platform to resolve the issue of data size and rich onboard memory and computing units. We have established a novel partition scheme of the 3D volume under reconstruction and corresponding multithread parallel acceleration strategy to fully utilize the computing res...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Zhu Y, Wang Q, Li M, Jiang M, Zhang P Tags: Phys Med Biol Source Type: research

IPEM Topical Report: A 2018 IPEM survey of MRI use for external beam radiotherapy treatment planning in the UK.
Conclusion:&amp;#13; The primary barriers reported to MRI implementation in EBRT planning included costs (e.g., lack of a national tariff for planning MRI), lack of MRI access and/or capacity within hospitals. Despite these challenges, significant interest remains in increasing MRI-assisted EBRT planning over the next five years.&amp;#13. PMID: 31239419 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Speight R, Schmidt MA, Liney GP, Johnstone R, Eccles CL, Dubec M, George B, Henry A, McCallum HM Tags: Phys Med Biol Source Type: research

A preclinical PET detector constructed with a monolithic scintillator ring.
Abstract This paper presents an unique preclinical positron emission tomography (PET) detector constructed with a monolithic scintillator ring (MSR) and two rings of silicon photomultipliers (SiPM). The inner diameter, outer diameter and length of the MSR were 48.5 mm, 58.5 mm, and 25.1 mm, respectively. The two SiPM rings, constructed with 46 SiPMs, were air-coupled to the two ends of the MSR detector. The center of gravity (COG) and artificial neural network (ANN) methods were adapted to decode the positions of the gamma interactions in the circumferential (θ) and axial (Z) directions, respectively. Collim...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Xu J, Xie S, Zhang X, Tao W, Yang J, Zhao Z, Weng F, Huang Q, Yi F, Peng Q Tags: Phys Med Biol Source Type: research

Development of a dosimetric model for < i > in vitro < /i > labelled cells with β+ emitters in PET tracking studies.
Development of a dosimetric model for in vitro labelled cells with β+ emitters in PET tracking studies. Phys Med Biol. 2019 Jun 26;: Authors: Jacquemin M, Broggio D, Franck D, Desbree A Abstract Positron emission tomography (PET) offers an effective method for tracking β+ emitters-labeled cells in vivo. However, in vitro high labelling activities used may cause cell damage or death. Our understanding of the impact of such procedure remains limited by the fact that the biological effects are usually linked to the activity per cell rather than the absorbed dose. To assess the dose delivered to...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Jacquemin M, Broggio D, Franck D, Desbree A Tags: Phys Med Biol Source Type: research

Experimental verification of a non-invasive method to monitor the lateral pencil beam position in an anthropomorphic phantom for carbon-ion radiotherapy.
M, Martisikova M Abstract The dose conformation and the sparing of neighboring critical healthy structures are improved in carbon-ion beam radiotherapy in comparison to conventional photon radiotherapy. Inter and intrafractional plan adaptation strategies may preclude the quality assurance (QA) of the actually applied treatment plan before the treatment starts. Therefore, independent measurements of the positions of scanned pencil &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C ion beams are of interest in order to monitor the beam application during the treatment and the beam in the isocenter. In this...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Félix-Bautista R, Gehrke T, Ghesquière-Diérickx L, Reimold M, Amato C, Turecek D, Jakubek J, Ellerbrock M, Martisikova M Tags: Phys Med Biol Source Type: research

On light sharing TOF-PET modules with depth of interaction and 157 ps FWHM coincidence time resolution.
Abstract The performance of a light sharing and recirculation mechanism that allows the extraction of depth of interaction (DOI) are investigated in this paper, with a particular focus on timing. In parallel, a method to optimize the coincidence time resolution (CTR) of PET detectors by use of the DOI information is proposed and tested. For these purposes, a dedicated 64-channels readout setup has been developed with intrinsic timing resolution of 16 ps FWHM. Several PET modules have been produced, based on LYSO:Ce scintillators and commercial silicon photomultiplier (SiPM) arrays, with 3x3 mm2 individual SiPM siz...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Pizzichemi M, Polesel A, Stringhini G, Gundacker S, Lecoq P, Tavernier S, Paganoni M, Auffray E Tags: Phys Med Biol Source Type: research

Quantitative characterization of breast tissues with dedicated CT imaging.
Abstract A quantitative characterization of the soft tissues composing the human breast is achieved by means of a monochromatic CT phase-contrast imaging system, through accurate measurements of their attenuation coefficients within the energy range of interest for breast CT clinical examinations. Quantitative measurements of linear attenuation coefficients are performed on tomographic reconstructions of surgical samples, using monochromatic X-ray beams from a synchrotron source and a free space propagation setup. An online calibration is performed on the obtained reconstructions, in order to reassess the validity...
Source: Physics in Medicine and Biology - June 24, 2019 Category: Physics Authors: Piai A, Contillo A, Arfelli F, Bonazza D, Brombal L, Cova MA, Delogu P, Di Trapani V, Donato S, Golosio B, Mettivier G, Oliva P, Rigon L, Taibi A, Tonutti M, Tromba G, Zanconati F, Longo R Tags: Phys Med Biol Source Type: research

Assessing lesion malignancy by scanning small-angle X-ray scattering of breast tissue with microcalcifications.
We report a characteristic Bragg peak found around q=1.725~nm&amp;lt;sup&amp;gt;-1&amp;lt;/sup&amp;gt; that occurs primarily for malignant lesions. Such a clear SAXS fingerprint is potentially linked to structural changes of the breast tissue and correspond to dimensions of about 3.7~nm. Such a material property could be used as an early indicator of malignancy development, as it is readily assessed by SAXS. If this fingerprint is combined with other known SAXS features, which also indicate the level of malignancy, such as lipid spacing and collagen periodicity, it could complement traditional pathology-bas...
Source: Physics in Medicine and Biology - June 24, 2019 Category: Physics Authors: Arboleda C, Lütz-Bueno V, Wang Z, Villanueva-Perez P, Guizar-Sicairos M, Liebi M, Varga Z, Stampanoni MFM Tags: Phys Med Biol Source Type: research